HAMR recording head having a sloped wall pole

ABSTRACT

An apparatus includes a waveguide having an end adjacent to an air bearing surface, first and second poles positioned on opposite sides of the waveguide, and wherein the first pole includes a first portion spaced from the waveguide and a second portion extending from the first portion to the air bearing surface, with the second portion being structured such that an end of the second portion is closer to the waveguide than the first portion.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with United States Government support underAgreement No. 70NANB1H3056 awarded by the National Institute ofStandards and Technology (NIST). The United States Government hascertain rights in the invention.

FIELD OF THE INVENTION

This invention relates to magnetic recording heads, and moreparticularly to such recording heads for use in heat assisted magneticrecording devices.

BACKGROUND OF THE INVENTION

In thermally assisted magnetic recording, information bits are recordedon a data storage medium at elevated temperatures, and the heated areain the storage medium determines the data bit dimension. In oneapproach, a beam of light is condensed to a small optical spot onto thestorage medium to heat a portion of the medium and reduce the magneticcoercivity of the heated portion. Data is then written to the reducedcoercivity region.

Heat assisted magnetic recording (HAMR) has been developed to addressinstabilities that result from a reduction in grain size in magneticrecording media. HAMR generally refers to the concept of locally heatinga storage medium to reduce the coercivity of the storage medium so thatan applied magnetic writing field can more easily direct themagnetization of the storage medium during the temporary magneticsoftening of the storage medium caused by the heat source. Heat assistedmagnetic recording allows for the use of small grain media, which isdesirable for recording at increased areal densities, with a largermagnetic anisotropy at room temperature to assure sufficient thermalstability.

One example of a recording head for use in heat assisted magneticrecording generally includes a write pole and a return pole magneticallycoupled to each other through a yoke or pedestal, and a waveguide forfocusing light onto the storage medium. One of the most challengingdesign requirements for an integrated HAMR head is in positioning themagnetic poles with respect to the focused spot in the waveguide.Magnetic materials such as alloys of Fe, Co and Ni are poor opticalmaterials, so they cannot be positioned in close proximity with thewaveguide for an appreciable distance.

There is a need for a magnetic pole design that reduces the probabilityof adjacent track writing and data destabilization.

SUMMARY OF THE INVENTION

In one aspect, this invention provides an apparatus including awaveguide having an end adjacent to an air bearing surface, and firstand second poles positioned on opposite sides of the waveguide, whereinthe first pole includes a first portion spaced from the waveguide and asecond portion extending from the first portion to the air bearingsurface, with the second portion being structured such that an end ofthe second portion is closer to the waveguide than the first portion.

The magnetic saturation of the second portion of the first pole can varyin a down track direction, either discretely using layers havingdifferent magnetic saturation, or continuously. The second portion ofthe first pole can have various cross-sectional shapes, and can includea plurality of sections.

The second pole can include a protrusion extending toward the secondportion of the first pole at the air bearing surface. A near fieldtransducer can be positioned in a core layer of the waveguide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial representation of a data storage device in theform of a disc drive.

FIG. 2 is a schematic representation of a slider and a storage medium.

FIG. 3 is a cross-sectional view of a recording head constructed inaccordance with an embodiment of the invention.

FIG. 4 is an enlarged view of a portion of the recording head of FIG. 3.

FIG. 5 is a plan view of the air bearing surface of the recording headof FIG. 3.

FIG. 6 is a graph of magnetic field versus distance for various polethicknesses.

FIG. 7 is an enlarged cross-sectional view of a portion of the recordinghead of FIG. 4.

FIG. 8 is a plan view of the air bearing surface of the recording headof FIG. 7.

FIG. 9 is a cross-sectional view of a portion of a recording head thatincludes a graded pole piece.

FIG. 10 is a plan view of a portion of the air bearing surface of therecording head of FIG. 9.

FIGS. 11 and 12 are graphs of finite element modeling (FEM) resultsshowing the magnetic field from a graded sloped pole.

FIG. 13 is a cross-sectional view of a recording head that includes atapered sloped pole piece.

FIG. 14 is a plan view of a portion of the air bearing surface of therecording head of FIG. 13.

FIG. 15 is a cross-sectional view of a recording head that includes atapered sloped pole piece.

FIG. 16 is a plan view of a portion of the air bearing surface of therecording head of FIG. 15.

FIG. 17 is a cross-sectional view of a recording head that includes atapered sloped pole piece.

FIG. 18 is a plan view of a portion of the air bearing surface of therecording head of FIG. 17.

FIG. 19 is a cross-sectional view of a recording head that includesanother sloped pole piece.

FIG. 20 is a plan view of a portion of the air bearing surface of therecording head of FIG. 19.

FIG. 21 is a cross-sectional view of another recording head thatincludes a sloped pole piece.

FIG. 22 is a plan view of a portion of the air bearing surface of therecording head of FIG. 21.

FIG. 23 is a top view of a recording head that includes a tapered slopedpole piece.

FIG. 24 is a top view of another recording head that includes a taperedsloped pole piece.

DETAILED DESCRIPTION OF THE INVENTION

This invention encompasses various devices used for heat assistedmagnetic recording. FIG. 1 is a pictorial representation of a datastorage device in the form of a disc drive 10 including a recording headconstructed in accordance with an aspect of this invention. The storagedevice includes a housing 12 (with the upper portion removed and thelower portion visible in this view) sized and configured to contain thevarious components of the disc drive. The disc drive includes a spindlemotor 14 for rotating at least one data storage medium 16 within thehousing, in this case a magnetic disc. At least one arm 18 is containedwithin the housing 12, with each arm 18 having a first end 20 with arecording and/or reading head or slider 22, and a second end 24pivotally mounted on a shaft by a bearing 26. An actuator motor 28 islocated at the arm's second end 24, for pivoting the arm 18 about apivot point to position the head 22 over a desired sector of the disc16. The actuator motor 28 is controlled by a controller that is notshown in this view and is well-known in the art. The storage mediumrotates in the direction indicated by arrow 30. As the disc rotates, theslider flies over the disc surface on an air bearing.

For heat assisted magnetic recording (HAMR), an electromagnetic wave of,for example, visible, infrared or ultraviolet light is directed onto asurface of a data storage medium to raise the temperature of a localizedarea of the medium to facilitate switching of the magnetization of thearea. Recent designs of HAMR recording heads include a thin filmwaveguide on a slider to guide light to the storage medium for localizedheating of the storage medium. To launch light into the waveguide, agrating coupler can be used.

FIG. 2 is a schematic representation of a portion of a suspension arm 32and slider 34, in combination with a magnetic recording disc 36. Duringwriting and/or reading of data, the disc moves relative to the slider ina direction indicated by arrow 38. The slider is coupled to thesuspension arm by a gimbal assembly 40 positioned adjacent to a surface42 of the disc and separated from the surface of the disc by an airbearing 44. The gimbal assembly includes a first portion 41 connected tothe suspension arm 32 and a second portion 42 connected to the slider34. The second portion is cantilevered to the first portion. The sliderhas a leading, or front, end 46 and a trailing, or back end 48. Theleading end faces toward the pivot point of the suspension arm and thetrailing end faces away from the pivot point of the suspension arm. Theslider includes an optical transducer 50 mounted adjacent to thetrailing end. A laser produces a beam of light illustrated by arrow 52that is transmitted toward the slider by an optical fiber 54. A mirror56 is mounted at the end of the suspension arm to reflect the lighttoward the optical transducer. The fiber is attached to the suspensionarm and terminates before the end of the suspension. The prism or mirrordirects the output from the fiber onto the transducer on the slider.Additional lenses may be necessary to maintain a small beam diameter.

FIG. 3 is a cross-sectional view of a recording head 100 constructed inaccordance with a first aspect of the invention. The recording headincludes a substrate 102, a base coat 104 on the substrate, a bottompole 106 on the base coat, and a top pole 108 that is magneticallycoupled to the bottom pole through a yoke or pedestal 110. A waveguide112 is positioned between the top and bottom poles. The waveguideincludes a core layer 114 and cladding layers 116 and 118 on oppositesides of the core layer. A mirror 120 is positioned adjacent to one ofthe cladding layers. The top pole is a two-piece pole that includes afirst portion, or pole body 122, having a first end 124 that is spacedfrom the air bearing surface 126, and a second portion, or sloped polepiece 128, extending from the first portion and tilted in a directiontoward the bottom pole. The second portion is structured to include anend adjacent to the air bearing surface 126 of the recording head, withthe end being closer to the waveguide than the first portion of the toppole. A planar coil 130 also extends between the top and bottom polesand around the pedestal. While this example includes a planar coil,other types of coils, such as a helical coil, could be used. A helicalcoil would wrap around the bottom/return pole. In alternativeembodiments, the planar coil could be positioned between the waveguideand the top pole.

An insulating material 132 separates the coil turns. Another layer ofinsulating material 134 is positioned adjacent to the top pole. In oneexample, the substrate can be AlTiC, the core layer can be Ta₂O₅, andthe cladding layers (and other insulating layers) can be Al₂O₃.

FIG. 4 is an enlarged cross-sectional view of a portion of the recordinghead of FIG. 3. FIG. 5 is a plan view of a portion of the air bearingsurface of the recording head of FIG. 3. When mounted in a data storagedevice, the recording head is positioned adjacent to a storage medium138, that moves with respect to the recording head as shown by the arrowin FIG. 4. A near field transducer 139 can be positioned adjacent to theair bearing surface to further concentrate light as it exits thewaveguide. In general, the near field transducer (NFT) would be locatedadjacent to the ABS and near the top pole. The NFT can be positioned inthe waveguide core, or the cladding, or between the waveguide core andthe cladding. The core-to-NFT spacing and/or the NFT-to-pole spacing canbe selected to achieve the desired performance of the NFT. Some types ofNFTs may not fit between the pole and the waveguide, but could belocated on the surface of the ABS. The NFT can be, for example, aplasmon resonator or an aperture. Plasmon resonators include, forexample, ridge waveguides, bow ties, pins, pins with disks, etc. In oneexample, the distance T_(c) between the first portion 122 of the pole108 and the core layer 114 of the waveguide 112 is at least 500 nm, andcan be about 1 μm. In another example, the distance T_(c) can beincreased to allow for positioning of the coil between the waveguide andthe top pole.

The structure of FIGS. 3, 4 and 5 tapers the second portion or slopedpole piece 128 of the top pole away from the waveguide core. As used inthis description, a sloped pole piece is a pole piece that has a firstend adjacent to the air bearing surface, and a second end magneticallycoupled to the body of the pole, wherein the first end is closer to thecore layer than the second end. In the example of FIGS. 3, 4 and 5, thesloped pole piece includes a single layer. The wall 137 of the slopedpole piece 128 forms an angle θ_(wall) with a plane 136 that is parallelto the core layer of the waveguide.

Finite Element Modeling was used to predict the field from the head ofFIGS. 3, 4 and 5. FIG. 6 shows the calculated resulting field. TheX-axis is the down track dimension, where X=0 is the leading edge of thepole. In a direction perpendicular to the ABS (i.e., along the Y-axis),the field value is calculated in a direction along the center of thepole, and at a point 10 nm below the ABS. The following inputs were usedin generating the graphs of FIG. 6: M_(s)=1.9 T, distance from ABS=10nm, NI=300 mA-Turns, μ of pole piece 106=500, μ of pole piece 128=100,θ_(wall)=30°.

FIGS. 7, 8, 9 and 10 show a series of designs that were modeled in anattempt to lower the field spike at the rear of the pole, increase thefield at the front face of the pole, or in general increase the ratio ofthe front face field to the back end field spike.

FIGS. 7 and 8 show a sloped pole piece 128. For this design, the wallangle (θ_(wall)), (that is, the angle between the wall of the slopedpole piece that is closest to the core layer and a plane parallel to thecore layer) can have a value between ˜15° and ˜75°. A smaller angle isbetter for the magnetics, but a larger angle is better for the optics.The thickness of the poles and the pole material can be varied in thedesign.

FIG. 9 is a cross-sectional view of a recording head that includes agraded pole piece 140. The graded pole piece includes a plurality oflayers 142, 144, 146, 148 and 150, each having a different magneticsaturation, M_(s). FIG. 10 is a plan view of a portion of the airbearing surface of the recording head of FIG. 9. FIGS. 9 and 10 show agraded M_(s) sloped pole piece design where the M_(s) of layer 150, nearthe waveguide core, has a large value (for example, 1.8 to 2.4 Tesla)and the magnetic saturation of the other layers decreases in the −Xdirection, using the coordinate system shown in FIG. 3. While theexample of FIGS. 9 and 10 shows distinct layers of magnetic materialhaving different magnetic saturation, the M_(s) of the sloped pole piececan be decreased continuously. In other examples, the entire top polecan be layered or can have a continuously varying magnetic saturation.

In one example of the graded sloped pole piece, a first layer of thepole piece that is close to the waveguide core layer can be 100 nm of1.9 T CoNiFe. A second layer that is adjacent to the first layer can be100 nm of 1.0 T NiFe. A third layer that is adjacent to the second layercan be 50 nm of 0.5 T NiCu. A fourth layer that is adjacent to the thirdlayer can be 50 nm of 0.3 T NiCu. A fifth layer that is adjacent to thefourth layer can be 50 nm of 0.1 T NiCu.

In another example, the first layer can be 50 nm of 2.4 T FeCo plus 50nm of CoNiFe. Then the second through fifth layers would be as describedabove.

FIGS. 11 and 12 are finite element modeling (FEM) results showing themagnetic field from the sloped pole. FIG. 11 shows the field in the Xand Y-directions: B_(x) and B_(y), using the coordinate system of FIG.3. FIG. 12 shows the effective field B_(eff).

In one example, the five layer graded M_(s) sloped pole design includeslayers having a M_(s) of: 0.1, 0.55, 1, 1.45 and 1.9 T for the curveslabeled M_(s)=1.9 T; and 0.1, 0.55, 1, 1.9 and 2.4 T for the curveslabeled M_(s)=2.4 T in FIGS. 11 and 12. The values of 1.9 T and 2.4 Tare for the magnetization of the layers closest to the waveguide core.It can be seen that the absolute and relative size of the field spikehas been reduced significantly.

The shape of the sloped pole piece as it extends from the pole body tothe ABS can be varied. FIG. 13 is a cross-sectional view of a recordinghead that includes a sharpened pole piece. FIG. 14 is a plan view of aportion of an air bearing surface of the recording head of FIG. 13. Inthis example, the sloped pole piece 160 includes a first portion 162having a uniform cross-sectional shape, and a second portion 164 that istapered as it extends to the air bearing surface 166. The sharpeningreduces the amount of pole material at the ABS.

FIG. 15 is a cross-sectional view of another recording head thatincludes a sloped pole piece. FIG. 16 is a plan view of a portion of anair bearing surface of the recording head of FIG. 15. In this example,the sloped pole piece 170 includes a uniform trapezoidal cross-sectionalshape as it extends to the air bearing surface 172. The sides 174 and176 of the sloped pole piece are tapered such that the width of thetrailing edge 178 of the sloped pole piece at the air bearing surface islarger than the width of the leading edge 180.

FIG. 17 is a cross-sectional view of a recording head that includes asloped pole piece. FIG. 18 is a plan view of a portion of the airbearing surface of the recording head of FIG. 17. In this example, thesloped pole piece 190 includes a uniform trapezoidal cross-sectionalshape as it extends to the air bearing surface 192. The sides 194 and196 of the sloped pole piece are tapered such that the width of theleading edge 200 of the sloped pole piece at the air bearing surface islarger than the width of the trailing edge 198.

FIGS. 15 and 16 show a trapezoidal sloped pole piece, and FIGS. 17 and18 show a reverse trapezoidal sloped pole piece. In these two cases, theshape of the pole is physically changed from the rectangular pole.

FIG. 19 is a cross-sectional view of another recording head thatincludes a sloped pole piece. FIG. 20 is a plan view of a portion of theair bearing surface of the recording head of FIG. 19. In this example,the sloped pole piece 210 includes a uniform rectangular cross-sectionalshape as it extends to the air bearing surface 216. However, the slopedpole piece includes a first portion 212 that is positioned at a firstangle θ₁ with respect to the core layer and a second portion 214 that ispositioned at a second angle θ₂ with respect to the core layer. FIGS. 19and 20 show a double slope pole piece. In the example of FIGS. 19 and20, the distance between the pole and the waveguide core increasesquickly with distance from the air bearing surface for good opticalefficiency, and then changes to a more gradual slope to help increasethe magnetic performance.

FIG. 21 is a cross-sectional view of a recording head that includes asloped pole piece. FIG. 22 is a plan view of a portion of an air bearingsurface of the recording head of FIG. 21. In this example, the slopedpole piece 220 has a uniform rectangular cross-sectional shape as itextends to the air bearing surface 218. However, the bottom pole 224includes a projection 226 at the air bearing surface 218 that extendstoward the sloped pole piece. FIGS. 21 and 22 show a design that bringsthe bottom pole up close to the sloped pole piece. This can help toreduce the flux divergence from the sloped pole piece before reachingthe front edge of the core as it extends to the return pole.

FIG. 23 shows a top down view of a recording head showing both thesloped pole piece 230 and the pole body 232 tapered in the X-direction.FIG. 24 shows a top down view of a recording head looking toward the ABSand showing both the sloped pole piece 230′ and the pole body 232′tapered in the X-direction. This helps to focus the flux as itapproaches the front edge of the sloped pole piece. There are optionswith respect to where the break point 234 or 234′ is located. It can beon the slope, at the very top of the slope, or on the surface. There canalso be more than one break point. In addition, the pole body can end atdifferent distances from the ABS. This can be measured with respect tothe sloped portion (i.e., the body extends to the slope or down onto theslope), or it can be measured with respect to the break points (i.e., itextends to the first break point).

It should be apparent that various aspects of the above designs could becombined with one another. For example, the trapezoidal pole can beconstructed as a graded M_(s) pole piece.

To prevent corrosion of the seed layer, the high moment (corrosive) seedlayer can be capped with a very thin NiFe layer. This NiFe layer needsto be kept very thin if the material being plated on top of the seedlayer has a moment >>1.0 Tesla. If the NiFe layer is too thick, the fluxwill escape from the pole at this point and cause a spike in the fieldunder the pole. If the material being plated on top of the high momentseed layer is ˜1.0 Tesla, the NiFe layer can be thicker. If the momentof the material being plated is <<1.0 Tesla, a different, more corrosionresistant material may be chosen as the capping layer, such as a Ni richNiFe, CoNi or CoNiFe alloy. In one example, layer 150 may be a seedlayer and a capping layer could be between layers 150 and 148. Inanother example, layers 150 and 148 could be seed layers and the cappinglayer could be between 148 and 146.

Some examples of material sets that can be used to construct the slopedpole piece are alloys including a first material “A” and a secondmaterial “B”, where A=Cu, Au, Ag or a combination of these three; andB═Fe, Co, Ni or a combination of these three. The alloy would be a mixof A and B materials. There could be multiple components of either A orB. The difference between the A and B materials is that the A materialsare more noble than the B materials, which allows for the adjusting ofthe composition. The moment (4πM_(s)) can be changed by changing thecontent of A. Increasing the A content can decrease moment.

While the invention has been described in terms of several examples, itwill be apparent to those skilled in the art that various changes can bemade to the described examples without departing from the scope of theinvention as set forth in the following claims.

1. A recording head comprising: a waveguide having an end adjacent to anair bearing surface; and a write pole and a return pole positioned onopposite sides of the waveguide; wherein the write pole includes a firstportion spaced from the waveguide and a second portion extending fromthe first portion to the air bearing surface, with the second portionbeing structured such that an end of the second portion is closer to thewaveguide than the first portion, and wherein the second portioncomprises an alloy including at least one of Cu, Au or Ag and at leastone of Fe, Co or Ni.
 2. The recording head of claim 1, wherein thesecond portion has a uniform cross-sectional shape.
 3. The recordinghead of claim 2, wherein the shape is rectangular.
 4. The recording headof claim 1, wherein the second portion is positioned at an angle withrespect to a core layer in the waveguide in the range of about 15° toabout 70°.
 5. The recording head of claim 1, wherein the first portionis separated from a core layer in the waveguide by at least 500 nm. 6.The recording head of claim 1, further comprising: a coil havingconductors positioned adjacent to the waveguide and on an opposite sideof the waveguide from the write pole.
 7. The recording head of claim 1,further comprising: a near field transducer.
 8. The recording head ofclaim 1, further comprising: a mirror positioned adjacent to thewaveguide.
 9. The recording head of claim 8, wherein the mirror ispositioned adjacent to a side of the waveguide opposite the write pole.10. The recording head of claim 1, wherein the thickness of the secondportion is smaller than the thickness of the first portion.
 11. Anrecording head comprising: a planar waveguide including a core layer andfirst and second cladding layers on opposite sides of the core layer,and having an end adjacent to an air bearing surface; and a write poleand a return pole positioned on opposite sides of the waveguide; whereinthe write pole includes a first portion spaced from the waveguide and asecond portion extending from the first portion to the air bearingsurface, with the second portion being structured such that an end ofthe second portion is closer to the waveguide than the first portion andwherein the second portion is positioned in the first cladding layer andat an angle with respect to the core in the range of about 15° to about70°.
 12. The recording head of claim 11, wherein the second portioncomprises an alloy including at least one of Cu, Au or Ag and at leastone of Fe, Co or Ni.
 13. The recording head of claim 11, wherein thesecond portion has a uniform cross-sectional shape.
 14. The recordinghead of claim 13, wherein the shape is rectangular.
 15. The recordinghead of claim 13, further comprising: a mirror positioned adjacent tothe waveguide.
 16. The recording head of claim 15, wherein the mirror isposition adjacent to a side of the waveguide opposite the write pole.17. The recording head of claim 11, wherein the thickness of the secondportion is smaller than the thickness of the first portion.
 18. Therecording head of claim 11, further comprising: a coil having conductorspositioned adjacent to the waveguide and on an opposite side of thewaveguide from the write pole.
 19. The recording head of claim 11,further comprising: a near field transducer.